Despite more than four years of study, the State Department's analysis of the project's environmental impact is "insufficient," the EPA said Monday.

In a letter to the State Department, the EPA urged State to conduct a more thorough analysis of oil spill risks and alternative pipeline routes, as well as greenhouse gas emissions associated with the $7 billion pipeline.

The concerns are similar to objections the EPA raised about the project in 2011. The State Department has authority over the pipeline because it crosses a U.S. border. A draft report in March said the project would not create significant environmental impacts.

The State Department said late Monday that officials have long planned to conduct additional analysis and will incorporate comments from the public and other federal agencies into a final environmental report expected this summer.